Making solidify modifier inside shape conform to the outside shape
I'm lacking the information I'd need for more than an guess, and it should be taken to account that I have less experience using the solidify modifier than certain others. That said, the first things I'd check are that:

you've applied scale and rotation to the object, before applying the solidify modifier;

you have the origin of the bottle object located in the center of the bottle object; and

you've chosen the proper pivot point before applying the modifier.